Property ownership law in michigan?

My 15 acres envelopes 2 smaller parcels of land owned by two separate home owners. One of these parcels, my land borders on three sides. The fourth side is the road. This neighbor asked one day if he could mow a 25' strip of my land the length of his property becuase i was just going to let it go to field. I allowed him to do that, it benefited me to have him mow it, and it benefitted him because it made his land look wider. Now, he has decided to take 30' the length of his property from the OTHER side... which was never offered to him. He has cut down trees, leveled it, parked his trailer on it, even moved his propane tank onto it. He has burnt it down and has had to have the fire dept called to put it out. I have warned him several times (even with property descriptions, aerial photos of the property boundaries and have had the land surveyed to show him exactly where his corner points are) that this was not okay, and don't know what to do now. He has his washing machine/sump pump discharge running onto my land and into my swamp. I'm not too disturbed by this part becuase its a swamp. BUT.... what do i do? Isn't there a law that if someone uses property for a certain amount of time, it becomes theres by default? i don't want to lose my property, and i don't know how to fend off his increasing land use.